We have collected data for four of five normal healthy volunteer subjects in this pilot study. There were no complications with exercise testing. Presently we are ensemble-averaging data from multiple exercise trials for each subject to improve mathematical modeling of the oxygen uptake response. In addition, we are examining alternative gas-exchange sampling procedures that may improve modeling ability without the need for multiple exercise trials. Continuance of this protocol is necessary to finish collection of pilot data to help determine the effect of exercise intensity on dynamic changes in VO2 during recovery from exercise.